Refrigerated cabinet and defrosting means



March 26, 1963 s. BECKWITH REFRIGERATEIj CABINET AND DEFROSTING MEANSFiled Feb. 13, 1961 oooooo ooooooo VENTOR.

afzfZ s United States Patent 3,082,612 REFRIGERATED CABINET ANDDEFROSTING MEANS This invention relates to the conditioning of anenclosed space having an open side for communication of the enclosedspace with the atmosphere and it relates more particularly tomaintaining a refrigerated state within the enclosed space having anopen side and which is used for the storage of food products and thelike.

In the copending application of Hagen et al., Ser. No. 54,077, filedSeptember 6', 1960, and entitled Refrigerated Display Case, and in theissued Simons Patent No. 2,862,369, description is made of arefrigerated display cabinet of the type described. Loss of heat fromthe refrigerated storage space through the open side is substantiallyobviated by the use of an air curtain which is advanced continuouslyacross the open side from one edge of the opening to the opposite edgein a manner to blanket the entire opening.

The air curtain is adapted to be formed of adjacent panels of air withthe inner panel comprising a refrigerated cold air panel and one or moreouter panels having temperatures more closely approaching the ambienttemperature from the inside out. For most eiiicient practice, it hasbeen found to be desirable to recirculate at least the inner cold airpanel and as many of the adjacent guard panels as possible thereby toconserve on the investment in the refrigeration required to maintain theotherwise enclosed space in the desired refrigerated state.

For example, in the Simons patent, use is made of an air curtain formedof but two panels comprising an inner cold air panel which isrefrigerated and continuously recirculated and an outer ambient airpanel which is cut off from the cold air panel at the opposite side ofthe access opening for return to the atmosphere. In the aforementionedcopending application of Hagen et al., illustration is made of amodified arrangement which makes use of an inner cold air panel and anouter panel both of which are recirculated through separate systems inthe cabinet whereby the outer panel acquires a temperature intermediatethe cold air panel and ambient temperature to function as a guard panelwhich minimizes heat loss while, at the same time, enhancing laminarfioW of the air panels making up the air curtain. Also disclosed in theaforementioned copending application of Hagen et al. is an arrangementwherein the curtain is formed of three recirculating panels inside-by-side relationship thereby further to increase the efficiency ofoperation from the standpoint of laminar flow characteristics and heatloss from the conditioned space.

In the aforementioned constructions, description is made of anarrangement wherein the nozzles extend across the bottom edge of theaccess opening to direct the air panels upwardly across the openingtowards inlets similarly extending across the top side of the accessopening. Description is also made of an arrangement wherein the nozzlesare located across the upper edge of the opening for projecting the airpanels downwardly across the opening to inlets arranged across thebottom side of the opening. It will be understood that the air nozzlescan also be located across one of the lateral edges of the opening fordirecting the corresponding air panels across the opening towards inletsin the opposite edge. Because of the more desirable effect of gravity onthe higher density cold air, it is preferred to flow the air curtaindownwardly from nozzles across the top to inlets across 3,082,612Patented Mar. 26, 1963 the bottom and the invention will hereinafter bedescribed with reference thereto, but it will be understood that theconcepts hereinafter described will also be applicable to otherdirections of flow.

It is an object of this invention to provide a method and means forimproving the operational characteristics as well as the flowcharacteristics of the refrigerated cabi net and it is a related objectto provide a method and means for the removal of frost separated outupon 8111', faces with which the cold air stream comes in contact andwhich, if not removed, might interfere with the desired flowcharacteristics for most efficient operation of the device.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawing, in which- FIG. 1 is a schematic sectional elevational view of arefrigerated cabinet embodying the features of this invention, and

FIG. 2 is a schematic sectional elevational view similar to that of FIG.1 illustrating a further modification in the cabinet construction.

Before entering into a discussion of the concepts of this invention, abrief description will be given of the cabinet and modificationsthereof.

Referring now to FIG. 1 of the drawing, the conditioning cabinet isprovided in the form of an enclosure having a top wall 12, a back wall14, a bottom wall 16, side walls (not shown) and a front wall IS. Thefront wall is provided with an access opening 20 of substantialdimension for communicating the enclosed space 22 within the interior ofthe cabinet with the outside atmosphere. The cabinet rests upon asuitable base 24.

Spaced inwardly from the outer walls of the housing and in substantiallyparallel relationship therewith are inner walls including a top wall 26,back wall 28, bottom wall 30, front wall 32 and side walls 34, all ofwhich define the storage space 22 therebetween. The space between theinner Walls and the outer Walls of the cabinet is subdivided in FIG. 1by a partitioning wall 36'to define two separated passages 38 and 40-which extend substantially continuously about the storage space 22 fromthe inlet openings 42 and 44 across one edge of the opening 2 h tooutlet openings 46 and 48 across the opposite edge of the opening.

The passage 38 is provided with refrigeration coils 50 through which asuitable refrigerant is circulated for passage in indirect heat exchangerelationship with the air traveling through the passage 38 for therefrigeration thereof. While refrigeration means 50 is illustrated asbeing located in the bottom run, adjacent the inlet to the passage, itwill be understood that the refrigeration means may be disposed in otherparts of the passage but preferably in the direction towards the inlet.

Located in advance of the refrigeration means 50 and preferably betweenthe refrigeration means and the inlet 42 is an air circulating meanssuch as a fan 52 or blower which operates to induce the flow of a streamof air through the passage 38 from the inlet 42 to the outlet 46 and, inaccordance with the concepts of this invention, from the outlet 46across the access opening 20 to the inlet 42 for recirculation of thecold air stream.

Similarly located Within the outer passage 40 is another air circulatingmeans 54, such as a fan or blower, for inducing the flow of air throughthe passage 40* from the inlet 44 to the outlet 48 and then, inaccordance with the concepts of this invention, from the outlet 48across the access opening to the inlet 44 for recirculation of the guardjet.

The outlets 46 and 48 are provided with nozzle members 56 and 58 adapteddirectionally to channel the air streams issued therefrom for laminarflow across the open space from the outlets to the inlets as previouslydescribed. For this purpose, it is desirable to make use of nozzles of avane construction, such as a honeycomb section; preferably. having aneffective length greater than about 1 inch and up to about 5 or 6inches. The streams of air issuing from the outlets 46 and 48 formcontinuous inner and outer air panels 60 and 62 which extend across theaccess opening Zilfrom the outlets to the inlets with the inner panel 69representing the refrigerated or cold air panel which is adapted tomaintain the storage space in a desired refrigerated state. Both of theinlets can be provided with screening members 64 to prevent theentrainment of solid materials, insects and the like into the passages.

From the foregoing brief description of the basic construction of therefrigerated cabinet, it will be apparent that there is provided aninner cold air panel 60 and an outer air panel 62 which will acquire atemperature intermediate the temperature of the cold air panel and theambient atmosphere. The guard panel 62 operates to guard the cold airfrom the heat of the atmosphere and to minimize the loss of cold airinto the atmosphere since air entrained from the guard panel into thecold air panel will be at considerably lower temperature than the airfrom the atmosphere which otherwise would be admixed. Further tominimize heat loss into the cold air recirculated through the passage38, it is desirable, though not essential, that the partitioning walls36 and the outer wall 14 be provided with suitable insulation, asdesignated by the numeral 66, and it is also preferred that the passage38 be separated from the storage space by an inner wall 26, 28 and 30having relatively good heat conductivity so that the cold air travelingthrough the passage 33 will be effective to refrigerate the space.

By way of still further modification, instead of making 2 use of asingle guard jet, additional guard jets may be provided whereby the airpanels extending across the ac- .cess opening 26 will correspond to thenumber of such jets. In the modification illustrated in FIG. *2, anadditional partition 68 is provided in the cabinet to make available athird passage 70 which is provided with a fan or blower 72 for therecirculation of an outer air stream through the passage 70 from aninlet 74 to an outlet 76 and, in accordance with the concepts of thisinvention, from the outlet 76 across the open space to the inlet 74.Thus the air curtain is formed with a third air panel 78 which islocated outwardly adjacent the panels 60 and 62,

For best practice in maintaining desirable laminar flow characteristicsbetween the panels, it is desirable to provide for air velocities withinthe range of about to 1,000 feet per minute and preferably Within therange of 100 to 400 feet per minute.

Because of the marked reduction that takes place in the temperature ofthe air as it shifts gradually from the ambient atmosphere into theouter air panel and from the outer air panel to the guard panel and fromthe guard panel to the cold air panel, it will be apparent that therelative humidity of the air will be increased with correspondingreduction in temperature to the extent that the air making up the guardjet and most likely the cold air panel will reach a state of completesaturation whereby frost formation will occur. Such a frost will usuallyseparate out onto surfaces engaged by the air stream and more preferablythe cold surfaces, such as the evaporator plates. 7

Such portions of frost or excess moisture as are not removed by therefrigeration coils will usually subsequently separate out on surfacesencountered by the moving stream of cold air, the most likely surfacebeing the ingoing side of the vaned or honeycombw sections forming thenozzles from which the airstreams are projected across the accessopening of the container. 7

It is an important concept. of this invention to provide asimple andefl'icient'means for rapid defrosting of the refrigerating coils withoutthe necessity completely to shut down the refrigeration of the cabinetand it is a further concept of this invention to effect snow or frostremoval from the vanes of the cold air nozzle and preferably to achievesuch snow or frost removal from the vanes in combination with thedefrost of the refrigerah ing coils thereby rapidly to recondition thecabinet for normal operation.

Forthis purpose, the cabinet is formed with one and preferably a numberof laterally spaced apart passages 80 communicating the ambientatmosphere with ports 8-2 in the walls of the passage 38 beyond theinlet 42 but before the circulating fan 52 and the refrigeration coils50. The passage 38 is provided with a shutter plate 84 pivoted on theouter wall above the ports 82 for rocking movement between a raisedposition to span the passage 38 for blocking the movement of airtherethrough while freeing the ports 82 to a lowered position whereinthe passage 38 is free for normal circulation of the cold air streamtherethrou-gh while the ports 82 are blocked. For this purpose, theshutter plate 84 is dimensioned to have a length corresponding to thelength of the passage and a width at least as great as the width of thepassage or the distance between the pivot and the far end of the ports82.

Another similar group of passages 86 communicate the ambient atmospherewith ports 88 in the walls of the passage 38 beyond the refrigerationcoils and preferably closely adjacent thereto. Another shutter plate 90is pivotal'ly mounted on the wall of the passage 38 above the ports '88for rocking movement between a raised position to extend across thepassage 38 for blocking the movement of air therethrough and freeing theports 88 to a lowered position for freeing the passage 38 for the flowof refrigerated air therethrough while blocking the ports 88. For thispurpose, the shutter plate 90 is dimensioned to have a lengthcorresponding to the length of the passage 3-8 and a width at least asgreat as the width of the passage 38 or the distance between the pivotand the far end of'the ports 88. The gates 84 and' 90 are adapted to beoperated together whereby the gates are both shifted to raised positiontogether so that the circulating fan 52 causes ambient air to be drawninto the passage 38 from the passage 80 and to be returned to theatmosphere through the ports 38 and the passage 86 until the warmambient air has been effective to achieve defrosting of therefrigeration coils 50, either by melting or by evaporation. The passage38 is provided with a drain 9-2 for venting the water that is producedupon defrosting of the coils.

Upon removal of the frost from the surfaces of the refrigeration coils50, the shutter plates 84 and 90 can be returned together to normal,lowered position whereby the cold air panel is reformed forrecirculation from the nozzles 46 across the access opening 20 to theinlets 42 to the passage 38 through which it is again recirculated pastthe defrosted refrigeration coils.

For rapid defrost, it is desirable to shut off the circulation ofrefrigerant to the evaporator coils 50. It is preferred, however, toshiftthe cold air channel from the inner panel to the adjacent panelduring the defrost cycle thereby to minimize the amount of temperaturerise that is permitted to take place in the refrigerated space. However,it is desirable to achieve this objective without interference with thedefrost cycle and without delay in the return of the elements to normaloperation. For this purpose, the guard passage 40 is provided with anauxiliary refrigerating coil $4 through which the re- 7 frigerant isbypassed when shut off from the main refrigerating coils 59 in thepassage 38 during thedefrost cycle. Thus the guard panel is abletemporarily to function as the cold air panel without'stopping operationof the device. Any frost collected on the evaporator coils in 'the guardpassage 40' will eventually be removed when 7 the guard passage isreturned to normal operation for the recirculation of air therethroughsince the air in the guard panel is usually at a temperature belowambient but above freezing temperature.

The period of defrost of the refrigeration means in the cold air passageaffords an opportunity for removal of snow or frost separated orotherwise collected on the vanes of the cold air nozzle 56 andparticularly on the ingoing side. For this purpose, the shutter plate 98is constructed to permit the passage of a slight flow of air beyond theplate for continued flow through the passage 38 to the nozzles on theout-going side thereof. Immediately in advance of the nozzles thepassage is provided with a heating element 95 of relatively smallcapacity, such as small resistance wires or heaters which are sufiicientto raise the temperature of the small amount of air which is permittedby the raised plate to continue to flow through the passage 38 but whichwould be relatively ineffective when confronted by the large volume ofcold air normally circulated through the passage when the shutter plateis lowered. Thus the heat is taken up by the slight flow of air forcarriage of heat to the vanes where the heat is eifective to melt thesnow or frost and provide for substantially complete removal thereof.

It will be understood that the shutter plate construction for blockingand unblocking the passages can be of other conventional constructions,such as slide gates or drawers or combinations thereof. It will befurther understood that the guard passage 40 need not be provided withauxiliary refrigeration means, especially when one or more other guardjets are employed in combination therewith since the defrost cycle canbe reduced to a matter of a few minutes, especially when heaters areemployed in advance of the fan 52 to increase the temperature of theambient air used to defrost and/or when the refrigeration cycle ismodified to circulate exhaust from the compressor through therefrigeration coils for more rapid defrost both internally by theexhaust and externally by the ambient air.

When a system is adopted to make use of the hot exhaust gases from thecompressor of the refrigeration system for circulation of the hot gasesthrough the evaporator coils St to accelerate defrost, the conceptheretofore described of using a heating element in advance of the coldair nozzle for preheating the small amount of air allowed to circulatepast the shutter plate can be eliminated. Instead, the residual heat inthe coils, immediately following defrost, will be sufiicient tointroduce enough heat in the initial portions of the air streamcontinued to be passed therethrough to effect the desired defrost of thenozzle vanes after the shutter $0 is returned to normal position.

It will be understood that the outlet nozzles may be positioned toextend across any of the sides of the openings with the inlet membersbeing positioned to extend across the opposite side for the passage ofthe air current crosswise therebetween.

It will also be understood that various changes may be made in thedetails of construction, arrangement and operation without departingfrom the spirit of the inven tion, especially as defined in thefollowing claims.

I claim:

1. In a refrigerated cabinet having an enclosed storage space with anaccess opening in one wall communicating the interior of the storagespace with the ambient atmosphere, adjacent inner and outer outletnozzles extending continuously across one side of the access opening andcorresponding inlet members extending continuously across the oppositeside of the access opening, inner and outer passages communicating withthe inlet members and the inner and outer outlet nozzles respectively,means for causing streams of air to flow through said passages from theinlets to the outlet nozzles and from the outlet nozzles as air panelsmaking up an air curtain flowing continuously across the access openingto the inlet members for recirculation through the passages,refrigeration means in the inner passage for refrigeration of the streamof air fiowing therethrough whereby the inner air panel of the aircurtain comprises a cold air panel, ports within said inner passagebefore and beyond said refrigeration means, means communicating saidports with the ambient atmosphere, and means shiftable in said innerpassage and associated with each of said ports for movement betweenunblocking position to blocln said ports and free said passages topermit normal flow of the cold air stream continuously through saidinner passage and blocking .position for blocking said passage andfreeing said ports for communication with the ambient atmosphere forflow of ambient air into said passage, through said refrigeration means,and then out of said passage for defrosting the refrigeration means.

2. A refrigerated cabinet as claimed in claim 1 in which the portscomprise one port located between the refrigeration means and the inletmember and another port located between the refrigeration means and theoutlet nozzle.

3. A refrigerated cabinet as claimed in claim 2 in which the means forcausing a stream of air to flow through the passage comprises a fanmeans located between the refrigeration means and the port beyond theinlet member.

4. A refrigerated cabinet as claimed in claim 1 which includes drainagemeans communicating with said refrigeration means for the removal ofmoisture upon melt ing the frost.

5. A refrigerated cabinet as claimed in claim 1 in which the outletnozzles are arranged in adjacent side-by-side parallel relation.

6. A refrigerated cabinet'as claimed in claim 5 in which the outletnozzles are arranged in side-by-side relation across the top of theaccess openingand the inlet members are arranged in side-by-siderelation across the bottom of the access opening.

7. A refrigerated cabinet as claimed in claim 1 in which the meansshiftable between blocking and unblocking position comprises a gatepivoted on the wall of the inner passage and dimensioned to have alength at least as great as the distance from the pivot to the farthestend of the port.

8. A refrigerated cabinet as claimed in claim 1 which includes a secondrefrigerating means in the adjacent passage.

9. A refrigerated cabinet as claimed in claim 8 which includes means forsupplying refrigerant to said refrigerating means in the cold airpassage and means for shutting off refrigerant from said refrigerationmeans in the cold air passage and by-passing thev refrigerant to therefrigeration means in the adjacent passage at about the same time thatthe blocking and unblocking means is shifted to blocking position andvice versa.

Brouse Apr. '12, 1949 Weber May 27, 1958

1. IN A REFRIGERATED CABINET HAVING AN ENCLOSED STORAGE SPACE WITH ANACCESS OPENING IN ONE WALL COMMUNICATING THE INTERIOR OF THE STORAGESPACE WITH THE AMBIENT ATMOSPHERE, ADJACENT INNER AND OUTER OUTLETNOZZLES EXTENDING CONTINUOUSLY ACROSS ONE SIDE OF THE ACCESS OPENING ANDCORRESPONDING INLET MEMBERS EXTENDING CONTINUOUSLY ACROSS THE OPPOSITESIDE OF THE ACCESS OPENING, INNER AND OUTER PASSAGES COMMUNICATING WITHTHE INLET MEMBERS AND THE INNER AND OUTER OUTLET NOZZLES RESPECTIVELY,MEANS FOR CAUSING STREAMS OF AIR TO FLOW THROUGH SAID PASSAGES FROM THEINLETS TO THE OUTLET NOZZLES AND FROM THE OUTLET NOZZLES AS AIR PANELSMAKING UP AN AIR CURTAIN FLOWING CONTINUOUSLY ACROSS THE ACCESS OPENINGTO THE INLET MEMBERS FOR RECIRCULATION THROUGH THE PASSAGES,REFRIGERATION MEANS IN THE INNER PASSAGE FOR REFRIGERATION OF THE STREAMOF AIR FLOWING THERETHROUGH WHEREBY THE INNER AIR PANEL OF THE AIRCURTAIN COMPRISES A COLD AIR PANEL, PORTS WITHIN SAID INNER PASSAGEBEFORE AND BEYOND SAID REFRIGERATION MEANS, MEANS COMMUNICATING SAIDPORTS WITH THE AMBIENT ATMOSPHERE, AND MEANS SHIFTABLE IN SAID INNERPASSAGE AND ASSOCIATED WITH EACH OF SAID PORTS FOR MOVEMENT BETWEENUNBLOCKING POSITION TO BLOCK SAID PORTS AND FREE SAID PASSAGES TO PERMITNORMAL FLOW OF THE COLD AIR STREAM CONTINUOUSLY THROUGH SAID INNERPASSAGE AND BLOCKING POSITION FOR BLOCKING SAID PASSAGE AND FREEING SAIDPORTS FOR COMMUNICATION WITH THE AMBIENT ATMOSPHERE FOR FLOW OF AMBIENTAIR INTO SAID PASSAGE, THROUGH SAID REFRIGERATION MEANS, AND THEN OUT OFSAID PASSAGE FOR DEFROSTING THE REFRIGERATION MEANS.